Field of the Invention
The present invention relates to a method of manufacturing a so-called drum-type core, comprising a conductive wire wound around a shaft part having flange parts on both ends, which is a magnetic body used for a wire-wound electronic component having a wound conductive wire, and more specifically to a drum core designed to increase the core density, prevent wire breakage or winding disorder, and improve the winding efficiency.
Description of the Related Art
With the popularity of mobile devices offering multiple functions and computerization of cars, so-called chip-type components that are small in size but still having a wound wire, are becoming increasingly common. Particularly in the area of coil components for power systems, a drum core having flange parts on both ends of a shaft part around which a wire is wound is used to support lower resistance, and there is a need for drum cores offering high performance and dimensional accuracy to support increasingly thinner components.
Methods of manufacturing the drum cores mentioned above include, for example, the method of manufacturing an inductance core disclosed in Patent Literature 1 below. This art is a method of manufacturing a core, which is called drum core, used for achieving inductance characteristics, where the method is based on a traditional grinding process. According to the traditional grinding process, however, the core part is formed by turning the work (compact) with reference to the outer periphery surfaces corresponding to the flange parts, so the outer periphery shape of the core part is roughly the same as the outer periphery shape of the flange part. For this reason, the aforementioned manufacturing method described in Patent Literature 1 is such that a rotational reference part is provided on the outer side of the part corresponding to each flange part and this rotational reference part is given an oval shape to give an oval shape to the core part. This method requires forming, grinding, and polishing in order to obtain the drum core shape. 
Additionally, Patent Literature 2 below discloses a method for press-forming a chip coil core. Use of press forming requires some ingenuity regarding dies, and under this art, an arc surface and press-receiving surface are provided on the dies used to form the winding core part in order to reduce damage to the dies. By winding a wire around a core thus formed, the wire can achieve closer contact with the winding core part compared with when a conventional winding core part of square or polygonal shape is used.